1. Field of the Invention
The invention relates to a local area network arrangement in accordance with the preamble of the attached claim 1. Unlike with conventional local area networks, in which performance (data transfer rate) is of importance, the local area network-of the invention is specifically intended for bidirectional transmission of slow data, in particular for bidirectional transmission of switch information (ON/OFF). The local area network arrangement of the invention is primarily developed for mains power control of real estates, but it also has other remarkable uses, such as access control systems and other monitoring or control systems. In the following, however, the background of the invention will be described with reference to an example of a mains control system of a real estate, as problems related to it have originally given an impulse to the invention.
2. Description of the Related Art
The greatest drawback of real estate electrification implemented in the conventional way is the fact that it does not enable "intelligent" installation that would allow flexible control and variability of the system. FIG. 1 illustrates the principle of the conventional installation technique. A separate conduit usually leads from a main distribution board 11 for each group of light fittings or wall sockets. In the figure, the number of the wires required is indicated with a number marked beside the cross line drawn across the wire, as usual; 2 or 3 wires are led to a switch 13 from each light fitting 12, and two wires are required for each group. In the example shown in the figure, a total number of 8 wires thus lead to the main distribution board (wall sockets are marked with reference number 14). An installation of this kind is simple, but also extremely fixed, and requires a professional for making modifications.